Sight flow apparatus such as sight flow windows and sight flow indicators are known which allow visual inspection of fluid flow through a fluid system. These sight flow apparatus generally comprise a body which is formed from, e.g., cast iron, steel or bronze. The body has an inlet and an outlet which are attached, e.g. threaded, bolted, soldered or welded, in-line with fluid pipes cooperatively forming a fluid flow line in a manufacturing plant or other facility. Transparent window(s) mounted to the side of the body allow visual inspection of the fluid flow through the sight flow apparatus, and hence the fluid flow within the fluid flow line. For example, one type of sight flow apparatus is a high pressure sight flow indicator manufactured by the assignee of the present invention under the Model No. F-910-HP.
Some sight flow apparatus have a fluid device or indicator, e.g., a rotor or a flapper, installed within the body. The rotor provides an indication of the direction and magnitude of fluid flow within the sight flow apparatus by the direction and rate of rotation of the rotor; while the flapper provides an indication of the direction and magnitude of fluid flow by the direction of the flapper and the angle at which the flapper extends. The rotor or flapper can be rotatably mounted on an axle extending between and supported by the windows on the body of the indicator, by the body itself, or by a pair of alignment washers located within the body. An example of a sight flow apparatus having a pair of alignment washers which support the axle for a flapper or rotor is shown and described in U.S. patent application Ser. No. 07/747,263 for "Sight Flow Indicator with Cartridge", also assigned to the assignee of the present invention and which is incorporated herein by reference.
One known type of rotor for the above-mentioned sight flow apparatus comprises an assembly of Teflon tubes which can be rotatably mounted on the axle in the sight flow apparatus. A plurality of round Teflon "plugs" are inserted through holes in the tube extending perpendicular to the axis of rotation. The plugs extend outward from both sides of the tube and are oriented in angular offset relation to each other. When the rotor is mounted on the axle, the surface area of the plugs provides resistance to fluids flowing through the body of the sight flow apparatus, which thereby rotates the rotor. When viewed through the window of the sight flow apparatus, the rotor provides a visual indication of the fluid flow through the fluid flow line.
However, the above-described rotor has certain drawbacks in that the rotor only rotates across a certain limited range of fluid flow rates. More particularly, this type of rotor has a tendency to stop turning when the rate of fluid flow through the sight flow apparatus drops below a certain level. This is believed to be due to the relatively large mass of the rotor concentrated around the rotational axis, and the round shape of the rotor plugs.
Moreover, the plugs on this type of rotor tend to be located centrally in the body to take advantage of the maximum fluid flow within the body of the sight flow product. However, mounting the plugs centrally in the body makes it difficult to visually inspect the rotation of the rotor through the windows of the apparatus--particularly when the fluid flowing through the sight flow apparatus is cloudy or dark. Accordingly, this type of rotor lacks flexibility in being able to provide an indication of fluid flow over a wide range of flow rates and conditions.
Another known type of rotor for the sight flow apparatus described above comprises a one-piece, paddle-wheel type body having radially extending vanes, such as shown and described in Moore, et al, U.S. Pat. No. 3,185,128. The Moore rotor is mounted on an axle extending between the windows in a sight-glass indicator. The direction and magnitude of fluid flow are provided by visually inspecting the rate of rotation of the vanes, and in particular the rotation of the edges of the vanes, through the window in the sight glass indicator.
However, the edges of the vanes in this type of rotor have a limited surface area which is visible through the windows in the sight glass indicator. Accordingly, it can also be difficult to visually inspect the rotation of the rotor through the window in this type of apparatus. Moreover, with either of the rotors described above, the large mass of the rotor tends to create a substantial pressure drop through the sight flow apparatus, which can be unacceptable in some situations.
Additionally, the dies for the integrally molded rotor and rotor parts described above can be expensive to purchase and maintain. These dies do not have the flexibility to quickly and easily provide rotors with different dimensions to enable the rotors to be installed within a wide variety of sight flow apparatus.
One known type of flapper for the above-described sight flow apparatus is also shown in the Moore patent. The Moore flapper includes a hollow tube which is rotatingly supported by the axle in the sight glass indicator. The tube includes an integrally attached, wing-like member, which extends outwardly from the tube and provides resistance to fluids flowing through the sight flow apparatus. The flapper is designed to rotate into the direction of fluid flow to provide an indication of the direction and magnitude of the fluid flow within the fluid line.
The above described flapper, however, also has certain drawbacks. For example, the flapper can only indicate horizontal and vertically upward fluid flow through the sight flow apparatus. The flapper normally hangs downwardly due to the force of gravity and rotates into the direction of fluid flow when fluid is present in the fluid line. However, if the sight flow apparatus is connected within a vertical fluid line, the flapper will still normally hang downward, and will thereby give an indication that fluid is flowing downwards through the fluid line, whether it is or not. Additionally, the edges of the flapper have a limited surface area visible through the windows in the sight glass indicator. Further, the dies for the integrally molded flapper can be expensive to purchase and maintain and do not have the flexibility to quickly and easily provide flappers with different dimensions to enable the flappers to be installed within a wide variety of sight flow apparatus.
Accordingly, there is a constant demand in the industry for sight flow apparatus with improved fluid indicator assemblies, and in particular, for sight flow apparatus which have improved rotor and/or flapper assemblies that facilitate visually inspecting the fluid flow through a fluid system over a wide range of flow rates, conditions and orientations. There is also a constant demand in the industry for fluid indicator assemblies which are simple to manufacture and which can be assembled rapidly and easily for installation within a wide variety of sight flow apparatus.